新研究對乳腺癌X光篩查提出進一步質疑

One of the largest and most meticulous studies of mammography ever done, involving 90,000 women and lasting a quarter century, has added powerful new doubts about the value of the screening test for women of any age.

歷史上規模最大、最嚴格細緻的乳房X光檢查研究之一，對所有年齡段的女性進行這種篩查的價值提出了強有力的新質疑。這項研究持續了四分之一個世紀之久，涉及9萬名女性。

It found that the death rates from breast cancer and from all causes were the same in women who got mammograms and those who did not. And the screening had harms — one out of five cancers found with mammography and treated was not a threat to the woman's health and did not need treatment like chemotherapy, surgery or radiation.

該研究發現，在做過乳房X線檢查和沒有做過它的女性中，乳腺癌導致的死亡率和所有原因導致的死亡率並無二致。而且這種篩查本身具有危害——通過乳房X光檢查發現並進行了治療的癌症腫塊中，有五分之一對女性的健康並不構成威脅，也不需要進行化療、手術或放療等治療。

The study, published Tuesday in The British Medical Journal, is one of the few rigorous evaluations of mammograms conducted in the modern era of more effective breast cancer treatments. It randomly assigned Canadian women to have regular mammograms and breast exams by trained nurses or to have breast exams alone.

這項研究本週二發表在《英國醫學雜誌》(BMJ)上，在如今這個乳腺癌治療手段更加有效的時代，對乳房X線檢查進行的嚴格評估寥寥無幾，它就是其中一個。在這項研究中，加拿大女性被隨機分配給訓練有素的護士，進行定期乳房X光檢查和乳房檢查，或者只進行乳房檢查。

Researchers sought to determine whether there was any advantage to finding breast cancers when they were too small to feel. The answer was no, the researchers report.

研究人員希望確定，在乳腺癌腫塊太小，患者感覺不到它的時候，發現乳腺癌是否有任何優勢。答案是否定的，研究報告稱。

The study seems likely to lead to an even deeper polarization between those who believe that regular mammography saves lives, including many breast cancer advocates and patients, and a growing number of researchers who say the evidence is lacking or, at the very least, murky.

這項研究很可能會導致更深的兩極分化：一方是相信定期做乳房X光檢查可以挽救患者生命的人，包括很多乳腺癌關愛活動倡導者和患者，另一方是越來越多的研究人員，他們認爲這種說法缺乏證據，或者至少是證據不明朗。

"It will make women uncomfortable, and they should be uncomfortable," said Dr. Russell P. Harris, a screening expert and professor of medicine at the University of North Carolina. "The decision to have a mammogram should not be a slam dunk."

“這會讓女性感到不舒服，她們也理應感到不舒服，”篩查專家、北卡羅萊納大學(University of North Carolina)醫學教授拉塞爾·P·哈里斯(Russell P. Harris)說。“決定做乳房X光檢查本來也不應該是一樁樂事。”

The findings will not lead to any immediate change in guidelines for mammography, and many advocates and experts will almost certainly dispute the idea that mammograms are on balance useless, or even harmful.

這些研究結果不會立刻導致乳房X光檢查準則的更改，很多倡導者和專家幾乎肯定會對“乳房X線檢查總體無用，甚至有害”的觀點進行質疑。

Dr. Richard C. Wender, chief of cancer control for the American Cancer Society, said the society has convened an expert panel that is reviewing all studies on mammography, including the Canadian one, and would issue revised guidelines later this year. He added that combined data from clinical trials of mammography showed it reduces the death rate from breast cancer by at least 15 percent for women in their 40s and by at least 20 percent for older women.

理查德·C·文德(Richard C. Wender)博士是美國癌症協會(American Cancer Society)癌症控制主任，他說該協會已經召集了一個專家小組，正在審查和乳房X光檢查有關的所有研究，加拿大的這項研究也包括在內，今年晚些時候，他們將發佈修訂後的準則。他還說，乳房X光檢查的臨牀試驗的綜合數據顯示，在40多歲的女性中，乳房X光檢查至少降低了15%的乳腺癌死亡率，在年齡更大的女性中降低了至少20%。

That means that one woman in 1,000 who starts screening in her 40s, two who start in their 50s and three who start in their 60s will avoid a breast cancer death, Dr. Harris said.

這意味着，在40多歲開始篩查的1000名女性中，有一名將避免死於乳腺癌，50歲開始的有兩名，60歲開始的有三名，哈里斯博士說。

Dr. Wender added that while improved treatments clearly helped lower the breast cancer death rate, so did mammography, by catching cancers early.

文德博士指出，改善後的治療方法顯然有助於降低乳腺癌死亡率，做乳房X光檢查也是一樣，因爲可以提早發現癌症。

But an editorial accompanying the new study said that earlier studies that found mammograms helped women were done before the routine use of drugs like tamoxifen that sharply reduced the breast cancer death rate. In addition, many studies did not use the gold-standard methods of the clinical trial, randomly assigning women to be screened or not.

但跟這項新研究同時發表的一篇社論說，那些發現乳房X光檢查有利於女性的早期研究，是在如今常規使用的藥物大幅降低乳腺癌死亡率之前進行的，這些藥物包括他莫昔芬(Tamoxifen)；此外，很多研究沒有采用標準最高的臨牀試驗方法，隨機分配女性是否接受篩查。

Dr. Mette Kalager, an epidemiologist and screening researcher at the University of Oslo and the Harvard School of Public Health who wrote the editorial, said there was a reason its results were unlike those of earlier studies. With better treatments, like tamoxifen, it was less important to find cancers early. Also, she said, women in the Canadian studies were aware of breast cancer and its dangers, unlike women in earlier studies who were more likely to ignore lumps.

這篇社論的作者梅特·卡拉格(Mette Kalager)博士是奧斯陸大學(University of Oslo)和哈佛大學公共衛生學院(Harvard School of Public Health)的流行病學家和篩查研究員，她表示，這項研究的結果不同於早期的那些研究是有原因的。有了更好的治療手段，比如他莫昔芬，提早發現癌症腫塊就不那麼重要了。此外她還表示，加拿大那項研究中的女性瞭解乳腺癌及其危險，而早期研究中的女性更有可能會忽視腫塊。

"It might be possible that mammography screening would work if you don't have any awareness of the disease," she said.

“如果你完全沒有乳腺癌的意識，乳房X光檢查就有可能效果不錯，”她說。

The Canadian study reached the same conclusion about the lack of a benefit from mammograms after 11 to 16 years of follow-up, but some experts predicted that as time went on the advantages would emerge.

在進行了11到16年的複查隨訪後，加拿大這項研究得出了乳房X線檢查沒有裨益的同樣結論。但一些專家預計，隨着時間的推移，乳房X線檢查的優勢將會顯現。

That did not happen, but with more time the researchers could, for the first time, calculate the extent of overdiagnosis, finding cancers that would never have killed the women but that led to treatments that included surgery, chemotherapy and radiation.

這種情況還沒有出現，但因爲多花了一些時間，研究人員首次計算出了過度診斷的程度，即針對絕不會令女性喪生的癌症腫塊，實施手術、化療和放療等治療手段。

Many cancers, researchers now recognize, grow slowly, or not at all, and do not require treatment. Some cancers even shrink or disappear on their own. But once cancer is detected, it is impossible to know if it is dangerous, so doctors treat them all.

研究人員現在認識到，很多癌症腫塊生長緩慢，或根本不生長，也不需要治療。有些癌症腫塊甚至會萎縮或自行消失。但是，一旦癌症腫塊被檢測到，你就不知道它是否會帶來危險，所以醫生會統統進行治療。

In the United States, about 37,000,000 mammograms are performed annually at a cost of about $100 per mammogram. Nearly three-quarters of women age 40 and over say they had a mammogram in the past year. More than 90 percent of women ages 50 to 69 in several European countries have had at least one mammogram.

美國每年大約要做3700萬例乳房X線檢查，每次檢查的費用約爲100美元（約合人民幣600元）。40歲及以上的女性有四分之三表示曾在過去一年裏進行過乳房X光檢查。在幾個歐洲國家，年齡在50至69歲的女性中有超過90%至少進行過一次乳房X光檢查。

Dr. Kalager, whose editorial accompanying the study was titled "Too Much Mammography," compared mammography to prostate-specific antigen screening for prostate cancer, using data from pooled analyses of clinical trials. It turned out that the two screening tests were almost identical in their overdiagnosis rate and had almost the same slight reduction in breast or prostate deaths.

卡拉格博士關於這項研究的社論標題是《乳房X光檢查氾濫》(Too Much Mammography)，文中使用來自臨牀試驗的彙總分析數據，把乳房X光檢查跟前列腺癌的前列腺特異性抗原（PSA）篩查相提並論。數據顯示，這兩種篩查的過度診斷率幾乎相同，在降低乳腺癌或前列腺癌死亡率的效果方面也幾乎同樣輕微。

"I was very surprised," Dr. Kalager said. She had assumed that the evidence for mammography must be stronger since most countries support mammography screening and most discourage PSA screening.

“我感到非常驚訝，”卡拉格博士說。她原以爲支持乳房X光檢查的證據肯定會更加有力，因爲大多數國家都支持乳房X光篩查，反對PSA篩查。